V$WAIT_CHAINS displays information about blocked sessions. A wait chain is comprised of sessions that are blocked by one another. Each row represents a blocked and blocker session pair. If a wait chain is not a cyclical wait chain, then the last row for the chain does not have a blocker.
| Column | Datatype | Description |
| CHAIN_ID | NUMBER | A number identifying the wait chain |
| CHAIN_IS_CYCLE | VARCHAR2(5) | Indicates whether the final blocked session in the wait chain is blocked by the initial blocked session (TRUE) or not (FALSE) |
| CHAIN_SIGNATURE | VARCHAR2(801) | An Oracle-specific text signature of the wait chain. This signature can be used to identify similar wait chains. |
| CHAIN_SIGNATURE_HASH | NUMBER | A numeric representation of CHAIN_SIGNATURE |
| INSTANCE | NUMBER | Blocked session's instance identifier |
| OSID | VARCHAR2(25) | Blocked session's operating system process identifier |
| PID | NUMBER | Blocked session's Oracle process identifier |
| SID | NUMBER | Blocked session's Oracle session identifier |
| SESS_SERIAL# | NUMBER | Blocked session's Oracle session serial number |
| BLOCKER_IS_VALID | VARCHAR2(5) | Indicates whether the blocked session has a blocker (TRUE) or not (FALSE) |
| BLOCKER_INSTANCE | NUMBER | Blocker session's instance identifier; NULL if BLOCKER_IS_VALID is FALSE |
| BLOCKER_OSID | VARCHAR2(25) | Blocker session's operating system process identifier; NULL if BLOCKER_IS_VALID is FALSE |
| BLOCKER_PID | NUMBER | Blocker session's Oracle process identifier; NULL if BLOCKER_IS_VALID is FALSE |
| BLOCKER_SID | NUMBER | Blocker session's Oracle session identifier; NULL if BLOCKER_IS_VALID is FALSE |
| BLOCKER_SESS_SERIAL# | NUMBER | Blocker session's Oracle session serial number; NULL if BLOCKER_IS_VALID is FALSE |
| BLOCKER_CHAIN_ID | NUMBER | If not NULL, then the blocker session is a member of another chain specified by this chain identifier. For the remaining wait chain information, see the wait chain with the specified CHAIN_ID. |
| IN_WAIT | VARCHAR2(5) | Indicates whether the blocked session is in a wait (TRUE) or not (FALSE) |
| TIME_SINCE_LAST_WAIT_SECS | NUMBER | Number of seconds since the last time the blocked session waited; NULL if IN_WAIT is TRUE |
| WAIT_ID | NUMBER | A number identifying the wait; NULL if IN_WAIT is FALSE |
| WAIT_EVENT | NUMBER | Resource or event number for which the blocked session is waiting; NULL if IN_WAIT is FALSE |
| WAIT_EVENT_TEXT | VARCHAR2(64) | Resource or event for which the blocked session is waiting; NULL if IN_WAIT is FALSE |
| P1 | NUMBER | First additional wait parameter; NULL if IN_WAIT is FALSE |
| P1_TEXT | VARCHAR2(64) | Description of the first additional wait parameter; NULL if IN_WAIT is FALSE |
| P2 | NUMBER | Second additional wait parameter; NULL if IN_WAIT is FALSE |
| P2_TEXT | VARCHAR2(64) | Description of the second additional wait parameter; NULL if IN_WAIT is FALSE |
| P3 | NUMBER | Third additional wait parameter; NULL if IN_WAIT is FALSE |
| P3_TEXT | VARCHAR2(64) | Description of the third additional wait parameter; NULL if IN_WAIT is FALSE |
| IN_WAIT_SECS | NUMBER | Seconds the blocked session has been in the current wait; NULL if IN_WAIT is FALSE |
| TIME_REMAINING_SECS | NUMBER | Seconds remaining until the blocked session ends its wait (-1 if the blocked session can indefinitely wait); NULL if IN_WAIT is FALSE |
| NUM_WAITERS | NUMBER | Number of sessions waiting for the blocked session |
| ROW_WAIT_OBJ# | NUMBER | Object ID for the table containing the row specified in ROW_WAIT_ROW#; NULL if IN_WAIT is FALSE |
| ROW_WAIT_FILE# | NUMBER | Identifier for the datafile containing the row specified in ROW_WAIT_ROW#; NULL if IN_WAIT is FALSE. This column is valid only if the blocked session is currently waiting for another transaction to commit and the value of ROW_WAIT_OBJ# is not -1. |
| ROW_WAIT_BLOCK# | NUMBER | Identifier for the block containing the row specified in ROW_WAIT_ROW#; NULL if IN_WAIT is FALSE. This column is valid only if the blocked session is currently waiting for another transaction to commit and the value of ROW_WAIT_OBJ# is not -1. |
| ROW_WAIT_ROW# | NUMBER | Current row being locked; NULL if IN_WAIT is FALSE. This column is valid only if the blocked session is currently waiting for another transaction to commit and the value of ROW_WAIT_OBJ# is not -1. |
Note:
1. V$WAIT_CHAINS is new in 11g.
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